This paper presents a rate control (RC) algorithm for the scalable extension of the H.264/AVC video coding standard. The proposed rate controller is designed for real-time video streaming with buffer constraint. Since a large buffer delay and bit rate variation are allowed in this kind of applications, our proposal reduces the quantization parameter (QP) fluctuation to provide consistent visual quality bit streams to receivers with a variety of spatio-temporal resolutions and processing capabilities. The low computational cost is another characteristic of the described method, since a simple lookup table is used to regulate the QP variation on a frame basis.